@Conditional-按照条件注册bean

@Conditional 通过改注解能判读根据条件动态创建bean

person类

public class Person {
    private String name;
    private int age;

    public Person() {
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }

    public Person(String name, int age) {

        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

配置类

import com.myspring.condition.linuxCondition;
import com.myspring.condition.windowsContidion;
import com.myspring.entity.Person;
import org.springframework.context.annotation.*;

@ComponentScan(value = "com.myspring")
@Configuration
public class MainConfig2 {

    @Conditional(windowsContidion.class)
    @Bean("bill")
    public Person person01(){
        return new Person("Bill Grate",62);
    }

    @Conditional(linuxCondition.class)
    @Bean("linus")
    public Person person02(){
        return new Person("linus",48);
    }
}

新建linuxCondition 实现 Condition 接口

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class linuxCondition implements Condition {

    /**
     * conditionContext 判读条件能使用的上下文
     *annotatedTypeMetadata 注解信息
     *
     */
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
         // 获取到bean的创建工程
        ConfigurableBeanFactory configurableBeanFactory  = conditionContext.getBeanFactory();
        // 获取类加载器
        ClassLoader loader = conditionContext.getClassLoader();

        // 获取环境
        Environment environment = conditionContext.getEnvironment();

        // 获取到bean定义的注册类
        BeanDefinitionRegistry beanDefinitionRegistry = conditionContext.getRegistry();

// 获取系统名称 
        String property = environment.getProperty("os.name");
        if(property.contains("linux")){
            return true;
        }

        return false;
    }
}

新建windowsCondition 实现 Condition 接口

package com.myspring.condition;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.env.Environment;
import org.springframework.core.type.AnnotatedTypeMetadata;

public class windowsCondition implements Condition {
    @Override
    public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
        // 获取环境
        Environment environment = conditionContext.getEnvironment();
        String property = environment.getProperty("os.name");
        if(property.contains("Windows")){
            return true;
        }
        return false;
    }
}

测试类

    @Test
    public void Test2()
    {

        ApplicationContext applicationContext = new AnnotationConfigApplicationContext(MainConfig2.class);
        String[] names  = applicationContext.getBeanDefinitionNames();
        for (String name : names) {
            System.out.println(name);
        }
         // 获取环境变量 Windows 10
        Environment environment = applicationContext.getEnvironment();
        String property = environment.getProperty("os.name");
        System.out.println(property);
        Map<String,Person> persons = applicationContext.getBeansOfType(Person.class);
        System.out.println(persons);
    }

运行结果
person
bill
备注
@Conditional 不仅能放在方法上也能放在类上。
当放在类上时，表明该类的创建都要符号该注解的条件

@Conditional-按照条件注册bean

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